1. Field of the Invention
This invention is concerned with the breaking or resolution of oil-in-water (O/W) bituminous emulsions by treatment with polymers of quaternary ammonium monomers.
2. Description of the Related Art
A great volume of hydrocarbons exist in known deposits of tar sands. These deposits occur at various places, the Athabasca tar sands in Canada being an example. The petroleum in a tar sand deposit is an asphaltic bitumen of a highly viscous nature ranging from a liquid to a semisolid. These bituminous hydrocarbons are usually characterized in being very viscous or even non-flowable under reservoir conditions by the application of driving fluid pressure.
Where surface mining is not feasible, the bitumen must be recovered by rendering the tar material mobile in-situ and producing it through a well penetrating the tar sand deposit. These in-situ methods of recovery include thermal, both steam and in-situ combustion and solvent techniques. Where steam or hot water methods are used, a problem results which aggravates the recovery of the bitumen. The difficulty encountered is emulsions produced by the in-situ operations. These emulsions are highly stable O/W emulsions which are made even more stable by the usual presence of clays. Most liquid petroleum emulsions are water-in-oil (W/O) types. These normal W/O emulsions are broken by methods known in the art. However, the bitumen emulsions which are O/W types present a much different problem, and the same demulsifiers used in W/O emulsions will not resolve the O/W bitumen emulsions. The uniqueness of these O/W bitumen emulsions is described in C. W. W. Gewers, J. Canad. Petrol. Tech., 7(2), 85-90 (1968). (Prior art Reference A.) There is much prior art concerning the resolution of normal W/O emulsions. Some of the art even mistakenly equates bitumen W/O emulsions with these W/O emulsions. The following is a list of several art references.
B. Texaco Canada was granted a recent patent, U.S. Pat. No. 4,058,453, for breaking bitumen emulsions using high molecular weight poly(ethylene oxides) of &gt;1,000,000 molecular weight with optional addition of alkaline earth metal halide. PA1 C. U.S. Pat. No. 4,141,854 claims the use of quaternary ammonium salts of co-polymers of acrylamide and dialkylaminoethylmethacrylate compounds (5-50 wt.% amino monomer units present) for breaking W/O emulsions encountered in uranium ore solvent extraction. To break O/W emulsions, it was necessary to first adjust the pH to 9 with NH.sub.3 and invert the emulsions with a surfactant (U.S. Pat. No. 4,154,698). PA1 D. In U.S. Pat. No. 4,120,815 a 50:50 wt.% copolymer of acrylamide (or acrylic acid) with diallyl dialkylammonium chloride was used to brek O/W emulsions encountered in refineries or waste treatment streams. PA1 E. In U.S. Pat. No. 4,160,742 co-polymers of acrylamide and methacrylamidopropyltrimethylammonium chloride (MAPTAC) (at least 50 wt.% acrylamide present) were used to break O/W oil refinery waste stream emulsions. PA1 F. U.S. Pat. No. 3,585,148 claims the use of acrylamide co-polymers with diallyl (or dimethallyl) dialkylammonium salts (containing no more than 25 wt.% quaternary salt) to break O/W emulsions. PA1 G. U.S. Pat. No. 4,224,150 describes a process for clarifying water containing oil or suspended solids by treatment with polymers of a quaternary ammonium monomer which has a structure different from that claimed by our invention. Further, the breaking of bitumen emulsions with the use of these polymers is not mentioned. The structure for the monomer in U.S. Pat. No. 4,224,150 is as follows: ##STR1##